EUV Spectroscopy of the Sunspot Region NOAA 7981 Using SOHO - I. Line Emission and Time Dependence
Harrison, R. A.; Wilhelm, K.; Fredvik, T.; Kjeldseth-Moe, O.; Haugan, S. V. H.; Brekke, P.; Thompson, W. T.; Pike, C. D.; Brynildsen, N.; Maltby, P.; Rimmele, T.
Norway, United Kingdom, United States, Germany
Abstract
EUV spectra of a medium-size sunspot and its surroundings, NOAA 7981, were obtained on 2 August 1996 with the Coronal Diagnostic Spectrometer (CDS) and the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) on the Solar and Heliospheric Observatory (SOHO). The spectral lines formed in the transition region and corona show considerable structure and large deviations from a uniform spatial distribution over the active region. Enhanced EUV emissions in transition region lines are concentrated in small regions outside the umbra of the sunspot throughout most of the observing sequence. Only during a short, active period do we find an enhanced line emission that reaches into the umbra. Preliminary values for the umbral intensity are given.